Gardening Tips: Birds and pesticides

The fall gardening season is in full swing as late season vegetables and flowers come into prominence.

I planted a combination of turnips, beets and carrots in my garden in an area that was vacated when I harvested my garlic in late July.

The turnips grew quickly and were ready to harvest less than a month after sowing. As I picked them, the slower to germinate beets began to grow and as I thinned them, the even slower growing carrots finally emerged.

It looks like I will harvest three types of root vegetables (four if I count the garlic) from the same raised bed. As a guy who is a serious “multi-tasker” this makes me a happy gardener!

The wild asters that seem to appear overnight at this time of year are putting on a spectacular display in the fields and roadsides the past two weeks.

I particularly enjoy the purple-flowered New England aster, but the various white and yellow species are also quite beautiful.

Asters have characteristic, daisy-like flowers that are usually small, but they appear in masses of clusters.

I plan to transplant some New England asters into a new perennial bed I am making in front of my house. I bet that with timely pinching during the growing season, these wild flowers will rival any greenhouse-grown varieties next fall.

I am also enjoying the masses of goldenrod blooming in uncut hay fields the past few weeks. Contrary to common belief, goldenrod is not a serious contributor to pollen-borne allergies, but the heavy yellow pollen is important food for bees and other pollinators.

Dahlias, anemones and chrysanthemums also provide lovely fall color in cultivated gardens and I noticed that some wild witch hazel shrubs are blooming in the woods. These spidery yellow blossoms also have an interesting, spicy fragrance.

Recently, a reader pointed me to a story regarding the effects of a particular class of pesticides called “neonicotinoids” on migrating songbirds.

These chemicals have come into widespread use in recent years since they are considered less toxic than some other products previously used.

Toxicity is a difficult concept to measure on all levels. All pesticides are thoroughly tested for acute toxicity and they are assigned what is known as an “LD 50.”

This term refers to the amount of the active ingredient that is needed to kill 50% of a test population, usually mice or rabbits. It is usually expressed as “parts per million” or milligrams per kilogram of body weight of the tested animals.

The lower the LD 50, the more acutely toxic the substance is. It is calculated for ingested as well as topical exposure.

Once this amount is calculated, smaller and smaller quantities are tested until a “NOEL” effect is established. NOEL means “No Observed Effect Level.”

The “NOEL” level is then divided by 1,000 to come up with an “acceptable” residue tolerance that may remain on the treated crop. This is a level that is considered “safe” for you and me to eat on a daily basis. Similar studies are used to calculate non-acute toxicity, primarily carcinogenicity. Even if a substance does not kill test animals outright, the substance must also be tested to see if it causes cancer, even in subsequent generations of the test animals.

One might think that with all this testing, once the product is allowed to be used, we can be pretty sure it is “safe.” Well, that is not always the case when it comes to non-targeted animals, such as birds and bees.

In the case of the “neonics,” the effect they have on migrating songbirds, who may eat as few as one corn seed that has been treated, is to cause them to stop feeding and lose body weight.

According to a story reported in the New York Times, this effect has led to an almost 20% decline in the overall populations of these birds. This same class of chemicals has also been linked to a major decline in bees and other pollinators. Right now millions of songbirds are migrating south and millions of people are also planting fall crops, especially lawn grasses.

I think that both farmers and homeowners should look carefully at the seed they may be planting right now to see if the seed has been treated with a product called “imidacloprid,” which is one of the most common neonics. If you use a lawn service, or employ a commercial operation that does this type of work, you might want to investigate this as well.

Reach Bob Beyfuss at rlb14@cornell.edu.